From: David Hildenbrand <david@redhat.com>
To: Baoquan He <bhe@redhat.com>
Cc: linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, linux-mm@kvack.org,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
"Michael S . Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH v1 1/6] mm/page_alloc: tweak comments in has_unmovable_pages()
Date: Wed, 29 Jul 2020 14:29:27 +0200 [thread overview]
Message-ID: <8a8c2306-3066-103a-17e1-22fb3b8484ba@redhat.com> (raw)
In-Reply-To: <20200729104753.GF14854@MiWiFi-R3L-srv>
On 29.07.20 12:47, Baoquan He wrote:
> On 07/28/20 at 04:07pm, David Hildenbrand wrote:
>> On 28.07.20 15:48, Baoquan He wrote:
>>> On 06/30/20 at 04:26pm, David Hildenbrand wrote:
>>>> Let's move the split comment regarding bootmem allocations and memory
>>>> holes, especially in the context of ZONE_MOVABLE, to the PageReserved()
>>>> check.
>>>>
>>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>>> Cc: Michal Hocko <mhocko@suse.com>
>>>> Cc: Michael S. Tsirkin <mst@redhat.com>
>>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>>> ---
>>>> mm/page_alloc.c | 22 ++++++----------------
>>>> 1 file changed, 6 insertions(+), 16 deletions(-)
>>>>
>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>> index 48eb0f1410d47..bd3ebf08f09b9 100644
>>>> --- a/mm/page_alloc.c
>>>> +++ b/mm/page_alloc.c
>>>> @@ -8207,14 +8207,6 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>>>> unsigned long iter = 0;
>>>> unsigned long pfn = page_to_pfn(page);
>>>>
>>>> - /*
>>>> - * TODO we could make this much more efficient by not checking every
>>>> - * page in the range if we know all of them are in MOVABLE_ZONE and
>>>> - * that the movable zone guarantees that pages are migratable but
>>>> - * the later is not the case right now unfortunatelly. E.g. movablecore
>>>> - * can still lead to having bootmem allocations in zone_movable.
>>>> - */
>>>> -
>>>> if (is_migrate_cma_page(page)) {
>>>> /*
>>>> * CMA allocations (alloc_contig_range) really need to mark
>>>> @@ -8233,6 +8225,12 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>>>>
>>>> page = pfn_to_page(pfn + iter);
>>>>
>>>> + /*
>>>> + * Both, bootmem allocations and memory holes are marked
>>>> + * PG_reserved and are unmovable. We can even have unmovable
>>>> + * allocations inside ZONE_MOVABLE, for example when
>>>> + * specifying "movable_core".
>>> ~~~~ should be 'movablecore', we don't
>>> have kernel parameter 'movable_core'.
>>
>> Agreed!
>>
>>>
>>> Otherwise, this looks good to me. Esp the code comment at below had been
>>> added very long time ago and obsolete.
>>>
>>> Reviewed-by: Baoquan He <bhe@redhat.com>
>>>
>>> By the way, David, do you know what is the situation of having unmovable
>>> allocations inside ZONE_MOVABLE when specifying 'movablecore'? I quickly
>>> went through find_zone_movable_pfns_for_nodes(), but didn't get why.
>>> Could you tell a little more detail about it?
>>
>> As far as I understand, it can happen that we have memblock allocations
>> during boot that fall into an area the kernel later configures to span
>> the movable zone (via movable_core).
>
> Seems yes, thanks a lot. Wondering who is still using
> movablecore|kernelcore in what use case.
>
AFAIK, it's the only (guaranteed) way to get ZONE_MOVABLE without
involving memory hotplug. As I learned, the movable zone is also
interesting beyond memory hotunplug. It limits unmovable fragmentation
and e.g., makes THP/huge pages more likely/easier to allocate.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-07-29 12:29 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-30 14:26 [PATCH v1 0/6] mm / virtio-mem: support ZONE_MOVABLE David Hildenbrand
2020-06-30 14:26 ` [PATCH v1 1/6] mm/page_alloc: tweak comments in has_unmovable_pages() David Hildenbrand
2020-07-28 13:48 ` Baoquan He
2020-07-28 14:07 ` David Hildenbrand
2020-07-29 10:47 ` Baoquan He
2020-07-29 12:29 ` David Hildenbrand [this message]
2020-06-30 14:26 ` [PATCH v1 2/6] mm/page_isolation: don't dump_page(NULL) in set_migratetype_isolate() David Hildenbrand
2020-07-28 13:56 ` Baoquan He
2020-07-29 17:31 ` Mike Kravetz
2020-07-29 18:08 ` David Hildenbrand
2020-07-29 18:35 ` Mike Kravetz
2020-07-29 18:41 ` David Hildenbrand
2020-07-30 4:21 ` Pankaj Gupta
2020-06-30 14:26 ` [PATCH v1 3/6] mm/page_isolation: drop WARN_ON_ONCE() " David Hildenbrand
2020-07-29 13:24 ` Baoquan He
2020-07-29 13:37 ` David Hildenbrand
2020-07-29 14:05 ` Baoquan He
2020-06-30 14:26 ` [PATCH v1 4/6] mm/page_isolation: cleanup set_migratetype_isolate() David Hildenbrand
2020-07-29 14:06 ` Baoquan He
2020-07-30 4:31 ` Pankaj Gupta
2020-06-30 14:26 ` [PATCH v1 5/6] mm/page_alloc: restrict ZONE_MOVABLE optimization in has_unmovable_pages() to memory offlining David Hildenbrand
2020-07-27 12:23 ` David Hildenbrand
2020-06-30 14:26 ` [PATCH v1 6/6] virtio-mem: don't special-case ZONE_MOVABLE David Hildenbrand
2020-07-21 9:59 ` [PATCH v1 0/6] mm / virtio-mem: support ZONE_MOVABLE David Hildenbrand
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